Touch panel and display device using the same

This application is related to commonly-assigned applications entitled, “TOUCH PANEL”, filed ______ (Atty. Docket No. US17449); “TOUCH PANEL”, filed ______ (Atty. Docket No. US17448); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17861); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17818); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17820); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17862); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17863); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US18263); “TOUCHABLE CONTROL DEVICE”, filed ______ (Atty. Docket No. US18262); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17889); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17884); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17885); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17886); “TOUCH PANEL, METHOD FOR MAKING THE SAME, AND DISPLAY DEVICE ADOPTING THE SAME”, filed ______ (Atty. Docket No. US17887); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17888); “TOUCH PANEL, METHOD FOR MAKING THE SAME, AND DISPLAY DEVICE ADOPTING THE SAME”, filed ______ (Atty. Docket No. US17865); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17864); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US18266); “METHOD FOR MAKING TOUCH PANEL”, filed ______ (Atty. Docket No. US18069); “METHOD FOR MAKING TOUCH PANEL”, filed ______(Atty. Docket No. US18068); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17841); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17859); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17860); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US17857); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US18258); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US18264); “TOUCH PANEL AND DISPLAY DEVICE USING THE SAME”, filed ______ (Atty. Docket No. US18267); “TOUCH PANEL, METHOD FOR MAKING THE SAME, AND DISPLAY DEVICE ADOPTING THE SAME”, filed ______ (Atty. Docket No. US17839); “ELECTRONIC ELEMENT HAVING CARBON NANOTUBES”, filed ______ (Atty. Docket No. US18066); and “TOUCH PANEL, METHOD FOR MAKING THE SAME, AND DISPLAY DEVICE ADOPTING THE SAME”, filed ______ (Atty. Docket No. US17858). The disclosures of the above-identified applications are incorporated herein by reference.

1. Field of the Invention

The present invention relates to a carbon nanotube based touch panel, and a display device incorporating the touch panel.

2. Discussion of Related Art

Following the advancement in recent years of various electronic apparatuses, such as mobile phones, car navigation systems and the like, toward high performance and diversification, there has been continuous growth in the number of electronic apparatuses equipped with optically transparent touch panels at the front of their respective display devices (e.g., liquid crystal panels). A user of any such electronic apparatus operates it by pressing or touching the touch panel with a finger, a pen, a stylus, or a like tool while visually observing the display device through the touch panel. Therefore, a demand exists for touch panels that are superior in visibility and reliable in operation.

At present, different types of touch panels, including resistance, capacitance, infrared, and surface sound-wave types have been developed. Due to their high accuracy and low cost of production, resistance-type touch panels have been widely used.

A conventional resistance-type touch panel includes an upper substrate, a transparent upper conductive layer formed on a lower surface of the upper substrate, a lower substrate, a transparent lower conductive layer formed on an upper surface of the lower substrate, and a plurality of dot spacers formed between the transparent upper conductive layer and the transparent lower conductive layer. The transparent upper conductive layer and the transparent lower conductive layer are formed of electrically conductive indium tin oxide (ITO).

In operation, an upper surface of the upper substrate is pressed with a finger, a pen, or a like tool, and visual observation of a screen on the liquid crystal display device provided on a back side of the touch panel is provided. This causes the upper substrate to be deformed, and the upper conductive layer thus comes in contact with the lower conductive layer at the position where the pressing occurs. Voltages are separately applied by an electronic circuit to the transparent upper conductive layer and the transparent lower conductive layer. Thus, the deformed position can be detected by the electronic circuit.

Each of the transparent conductive layers (e.g., ITO layers) is generally formed by means of ion-beam sputtering, and this method is relatively complicated. Additionally, the ITO layer has poor wearability/durability, low chemical endurance, and uneven resistance over an entire area of the touch panel. Furthermore, the ITO layer has relatively low transparency. All the above-mentioned problems of the ITO layer make for a touch panel with low sensitivity, accuracy, and brightness.

What is needed, therefore, is to provide a durable touch panel and a display device using the same with high sensitivity, accuracy, and brightness.

In one embodiment, a touch panel includes a first electrode plate, and a second electrode plate separated from the first electrode plate. The first electrode plate includes a first substrate, a first conductive layer, and at least two electrodes. The first conductive layer and the at least two electrodes are located on a lower surface of the first substrate. The at least two electrodes are located on the first electrode plate and electrically connected with the first conductive layer. The second electrode plate includes a second substrate, a second conductive layer, and at least two electrodes. The second conductive layer and the at least two electrodes are located on an upper surface of the second substrate. The at least two electrodes are located on the second electrode plate and electrically connected with the second conductive layer. At least one of the first and second conductive layers includes a plurality of carbon nanotube wire-like structures. Two ends of each carbon nanotube wire-like structure are connected with two of the electrodes.

Other novel features and advantages of the present touch panel and display device using the same will become more apparent from the following detailed description of exemplary embodiments, when taken in conjunction with the accompanying drawings.

Corresponding reference characters indicate corresponding parts throughout the views. The exemplifications set out herein illustrate at least one embodiment of the present touch panel and display device using the same, in at least one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

Reference will now be made to the drawings to describe, in detail, embodiments of the present touch panel and display device using the same.

Referring to FIG. 1 and FIG. 2, a touch panel 10 includes a first electrode plate 12, a second electrode plate 14, and a plurality of dot spacers 16 located between the first electrode plate 12 and the second electrode plate 14.

The first electrode plate 12 includes a first substrate 120, a first conductive layer 122, and at least two first-electrodes 124. The first substrate 120 has an upper surface and a lower surface, and the upper surface and the lower surface are substantially flat. In the illustrated embodiment, there are multiple first-electrodes 124. The first-electrodes 124 and the first conductive layer 122 are located on the lower surface of the first substrate 120. The first-electrodes 124 are arranged in two parallel columns at opposite ends of the lower surface of the first substrate 120, and are electrically connected with the first conductive layer 122. The first conductive layer 122 is arranged on the lower surface of the first substrate 120. That is, the two columns of first-electrodes 124 are located at opposite ends of the first conductive layer 122 respectively. A direction from one of the columns of first-electrodes 124 across the first conductive layer 122 to the other column of first-electrodes 124 is defined as a first direction.

The second electrode plate 14 includes a second substrate 140, a second conductive layer 142, and at least two second-electrodes 144. The second substrate 140 includes an upper surface and a lower surface, and the upper surface and the lower surface are substantially flat. In the illustrated embodiment, there are multiple second-electrodes 144. The second-electrodes 144 and the second conductive layer 142 are located on the upper surface of the second substrate 140. The second-electrodes 144 are arranged in two parallel columns at opposite ends of the upper surface of the second substrate 140 respectively, and are electrically connected with the second conductive layer 142. The second conductive layer 142 is arranged on a major portion of the upper surface of the second substrate 140. That is, the two columns of second-electrodes 144 are located at opposite ends of the second conductive layer 142 respectively. A direction from one of the columns of second-electrodes 144 across the second conductive layer 142 to the other column of second-electrodes 144 is defined as a second direction.

The first direction is perpendicular to the second direction; i.e., the columns of first-electrodes 124 are orthogonal to the columns of second-electrodes 144. The first substrate 120 is a transparent and flexible film/plate. The second substrate 140 is a transparent plate. The first-electrodes 124 and the second-electrodes 144 are made of metal or any other suitable conductive material. In the present embodiment, the first substrate 120 is a polyester film, the second substrate 140 is a glass plate, and the first-electrodes 124 and the second-electrodes 144 are made of a conductive silver paste.

An insulative layer 18 is provided between the first and second substrates 120, 140. In the illustrated embodiment, the insulative layer 18 is in the form of a rectangular bead. The first electrode plate 12 is located on the insulative layer 18. That is, the first conductive layer 122 faces, but is spaced from, the second conductive layer 142. The dot spacers 16 are located on the second conductive layer 142. A distance between the second electrode plate 14 and the first electrode plate 12 is typically in an approximate range from 2 to 20 microns. The insulative layer 18 and the dot spacers 16 are made of, for example, insulative resin or any other suitable insulative material. Electrical insulation between the first electrode plate 12 and the second electrode plate 14 is provided by the insulative layer 18 and the dot spacers 16. It is to be understood that the dot spacers 16 are optional, particularly when the size of the touch panel 10 is relatively small.

In the present embodiment, a transparent protective film 126 is located on the upper surface of the first electrode plate 12. The material of the transparent protective film 126 can be selected from a group consisting of silicon nitrides, silicon dioxides, benzocyclobutenes, polyester films, and polyethylene terephthalates. For example, the transparent protective film 126 can be made of slick plastic and receive a surface hardening treatment to protect the first electrode plate 12 from being scratched when in use.

At least one of the first conductive layer 122 and the second conductive layer 142 includes a plurality of carbon nanotube wire-like structures. A plurality of the first-electrodes 124 and/or the second-electrodes 144 is located on opposite ends of the corresponding electrode plate 12, 14 having the plurality of carbon nanotube wire-like structures formed thereon. Two ends of each carbon nanotube wire-like structure are connected with two opposite first-electrodes 124 and/or second-electrodes 144 respectively. That is, each corresponding first-electrode 124 and/or second-electrode 144 is connected with the end of at least one carbon nanotube wire-like structure. The carbon nanotube wire-like structure can be a carbon nanotube wire. Referring to FIG. 3, each carbon nanotube wire is comprised of a plurality of successive carbon nanotubes joined end to end by van der Waals attractive force therebetween. Lengths of the carbon nanotube wires can be arbitrarily set as desired. The carbon nanotube wires can be parallel to and spaced apart from each other. A diameter of each carbon nanotube wire is in an approximate range from 0.5 nanometers to 100 micrometers (μm). Distances between adjacent carbon nanotube wires are in an approximate range from 10 nanometers to 1 millimeter. The carbon nanotubes in the carbon nanotube wires can be selected from a group consisting of single-walled, double-walled, and multi-walled carbon nanotubes. A diameter of each single-walled carbon nanotube is in an approximate range from 0.5 nanometers to 50 nanometers. A diameter of each double-walled carbon nanotube is in an approximate range from 1 nanometer to 50 nanometers. A diameter of each multi-walled carbon nanotube is in an approximate range from 1.5 nanometers to 50 nanometers.

In the present embodiment, the first conductive layer 122 and the second conductive layer 142 both include a plurality of carbon nanotube wire-like structures. The carbon nanotube wire-like structure is a carbon nanotube wire. The carbon nanotube wires are parallel to each other and spaced apart from each other. The carbon nanotube wires in the first conductive layer 122 cross the carbon nanotube wires in the second conductive layer 142. That is, the carbon nanotube wires in the first conductive layer 122 are aligned along the first direction, and the carbon nanotube wires in the second conductive layer 142 are aligned along the second direction. In this embodiment, the first direction is perpendicular to the second direction. In other embodiments, the first direction can be set at an angle other than perpendicular (oblique) to the second direction.

A method for fabricating the above-described first conductive layer 122 and second conductive layer 142 includes the steps of: (a) providing an array of carbon nanotubes or providing a super-aligned array of carbon nanotubes; (b) pulling out a carbon nanotube structure from the array of carbon nanotubes, by using a tool (e.g., adhesive tape, pliers, tweezers, or another tool allowing multiple carbon nanotubes to be gripped and pulled simultaneously); and (c) treating the carbon nanotube structure with an organic solvent or mechanical force to form a carbon nanotube wire; and (d) placing a plurality of the carbon nanotube wires in parallel and space apart from one another on each of the first substrate 120 and the second substrate 140, thereby forming a first conductive layer 122 on the first substrate 120 and a second conductive layer 142 on the second substrate 140.

The method of fabricating a nanotube film comprises steps (a) and (b). A nanotube film can be used as a shielding layer.

In step (a), a given super-aligned array of carbon nanotubes can be formed by the substeps of: (a1) providing a substantially flat and smooth substrate; (a2) forming a catalyst layer on the substrate; (a3) annealing the substrate with the catalyst layer in air at a temperature in an approximate range from 700° C. to 900° C. for about 30 to 90 minutes; (a4) heating the substrate with the catalyst layer to a temperature in the approximate range from 500° C. to 740° C. in a furnace with a protective gas therein; and (a5) supplying a carbon source gas to the furnace for about 5 to 30 minutes and growing the super-aligned array of carbon nanotubes on the substrate.

In step (a1), the substrate can be a P-type silicon wafer, an N-type silicon wafer, or a silicon wafer with a film of silicon dioxide thereon. In this embodiment, a 4-inch P-type silicon wafer is used as the substrate.

In step (a2), the catalyst can be made of iron (Fe), cobalt (Co), nickel (Ni), or any alloy thereof.

In step (a4), the protective gas can be made up of at least one of nitrogen (N2), ammonia (NH3), and a noble gas. In step (a5), the carbon source gas can be a hydrocarbon gas, such as ethylene (C2H4), methane (CH4), acetylene (C2H2), ethane (C2H6), or any combination thereof.

The super-aligned array of carbon nanotubes can have a height of about 50 microns to 5 millimeters and include a plurality of carbon nanotubes parallel to each other and approximately perpendicular to the substrate. The carbon nanotubes in the array of carbon nanotubes can be selected from a group consisting of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes. A diameter of each single-walled carbon nanotube approximately ranges from 0.5 nanometers to 50 nanometers. A diameter of each double-walled carbon nanotube approximately ranges from 1 nanometer to 50 nanometers. A diameter of each multi-walled carbon nanotube approximately ranges from 1.5 nanometers to 50 nanometers.

The super-aligned array of carbon nanotubes formed under the above conditions is essentially free of impurities such as carbonaceous or residual catalyst particles. The carbon nanotubes in the super-aligned array are closely packed together by the van der Waals attractive force.

In step (b), the carbon nanotube structure can be formed by the substeps of: (b1) selecting a plurality of carbon nanotube segments having a predetermined width from the array of carbon nanotubes; and (b2) pulling the carbon nanotube segments at an even/uniform speed to achieve a uniform carbon nanotube structure.

In step (b1), the carbon nanotube segments can be selected by using a tool, such as adhesive tapes, pliers, tweezers, or another tools allowing multiple carbon nanotubes to be gripped and pulled simultaneously to contact with the super-aligned array. Referring to FIG. 4 and FIG. 5, each carbon nanotube segment 143 includes a plurality of carbon nanotubes 145 parallel to each other, and combined by van der Waals attractive force therebetween. The carbon nanotube segments 145 can vary in width, thickness, uniformity and shape. In step (b2), the pulling direction is substantially perpendicular to the growing direction of the super-aligned array of carbon nanotubes.

More specifically, during the pulling process, as the initial carbon nanotube segments 143 are drawn out, other carbon nanotube segments 143 are also drawn out end to end due to the van der Waals attractive force between ends of adjacent carbon nanotube segments 143. This process of drawing ensures a continuous, uniform carbon nanotube structure can be formed. The pulling/drawing method is simple, fast, and suitable for industrial applications.

In step (c), the carbon nanotube structure is soaked in an organic solvent. Since the untreated carbon nanotube structure is composed of a number of carbon nanotubes 145, the untreated carbon nanotube structure has a high surface area to volume ratio and thus may easily become stuck to other objects. During the surface treatment, the carbon nanotube structure is shrunk into a carbon nanotube wire after the organic solvent volatilizing, due to factors such as surface tension. The surface area to volume ratio and diameter of the treated carbon nanotube wire is reduced. Accordingly, the stickiness of the carbon nanotube structure is lowered, and strength and toughness of the carbon nanotube structure is improved. The organic solvent may be a volatilizable organic solvent, such as ethanol, methanol, acetone, dichloroethane, chloroform, and any combination thereof. A diameter of the carbon nanotube wires approximately ranges from 0.5 nanometers to 100 micrometers (μm).

In step (c), the carbon nanotube structure also can be treated with mechanical force (e.g., a conventional spinning process), to acquire a carbon nanotube wire in a twisted shape.

In step (d), the distances between the adjacent carbon nanotube wires can be set according to the desired optical transparency properties of the touch panel 10. In the present embodiment, the distances between the adjacent carbon nanotube wires are in an approximate range from 10 nanometers to 1 millimeter. Further, all the adjacent carbon nanotube wires are spaced apart a same distance.

Two ends of each of the carbon nanotube wires in the first conductive layer 122 are connected with two corresponding opposite first-electrodes 124, and two ends of each of the carbon nanotube wires in the second conductive layer 142 are connected with two corresponding opposite second-electrodes 144. Each first-electrode 124 and second-electrode 144 is connected with the end of at least one carbon nanotube wire. In the present embodiment, each first-electrode 124 is connected with the end of only one carbon nanotube wire in the first conductive layer 122, and each second-electrode 144 is connected with the end of only one carbon nanotube wire in the second conductive layer 142. In this embodiment, the carbon nanotube wires in the first conductive layer 122 are spaced apart, and each carbon nanotube wire is arranged along the first direction. Alternatively, each carbon nanotube wire in the first conductive layer 122 can stray from the first direction. In this embodiment, the carbon nanotube wires in the second conductive layer 142 are spaced apart, and each carbon nanotube wire is arranged along the second direction. The first direction is perpendicular to the second direction. Alternatively, each carbon nanotube wire in the second conductive layer 142 can deflect from the second direction. The plurality of first-electrodes 124 and second-electrodes 144 are connected with a circuit of the touch panel 10 via electrode down-leads.

Referring also to FIG. 6, the touch panel 10 can further include a shielding layer 22 located on the lower surface of the second substrate 140. The material of the shielding layer 22 can be selected from a group consisting of indium tin oxides, antimony tin oxides, carbon nanotube films, and other conductive materials. In the present embodiment, the shielding layer 22 is a carbon nanotube film. The carbon nanotube film includes a plurality of carbon nanotubes, and the orientations of the carbon nanotubes therein can be arbitrarily set as desired. In this embodiment, the carbon nanotubes in the carbon nanotube film of the shielding layer 22 are arranged along a same direction. The carbon nanotube film is connected to ground and acts as a shield, thus enabling the touch panel 10 to operate without interference (e.g., electromagnetic interference).

An exemplary display device 100 includes the touch panel 10, a display element 20, a first controller 30, a central processing unit (CPU) 40, and a second controller 50. The touch panel 10 is opposite and adjacent to the display element 20, and is connected to the first controller 30 by a circuit external to the touch panel 10. The touch panel 10 can be spaced from the display element 20 or installed directly on the display element 20. In the present embodiment, the touch panel 10 is spaced from the display element 20. That is, the touch panel 10 and the display element 20 are spaced apart and separated by a gap 26. The first controller 30, the CPU 40, and the second controller 50 are electrically connected. In particular, the CPU 40 is connected to the second controller 50 to control the display element 20.

The display element 20 can be, e.g., a liquid crystal display, a field emission display, a plasma display, an electroluminescent display, a vacuum fluorescent display, a cathode ray tube, or another display device.

When the shielding layer 22 is located on the lower surface of the second substrate 140, a passivation layer 24 is located on a surface of the shielding layer 22 that faces away from the second substrate 140. The material of the passivation layer 24 can, for example, be silicon nitride or silicon dioxide. The passivation layer 24 can protect the shielding layer 22 from chemical or mechanical damage.

In typical operation of the display device 100, a 5V (volts) voltage is applied to the two columns of first-electrodes 124 of the first electrode plate 12, and to the two columns of second-electrodes 144 of the second electrode plate 14. A user operates the display device 100 by pressing the first electrode plate 12 of the touch panel 10 with a finger 60, a pen/stylus 60, or the like, while visually observing the display element 20 through the touch panel 10. This pressing causes a deformation 70 of the first electrode plate 12. The deformation 70 of the first electrode plate 12 establishes an electrical connection between the first conductive layer 122 of the first electrode plate 12 and the second conductive layer 142 of the second electrode plate 14. Changes in voltages along the first direction of the first conductive layer 122 and along the second direction of the second conductive layer 142 can be detected by the first controller 30. Then the first controller 30 transforms the changes in voltages into coordinates of the pressing point, and sends the coordinates to the CPU 40. The CPU 40 then sends out commands according to the coordinates of the pressing point. Thereby, the user can control the display of the display element 20.

The properties of the carbon nanotubes provide superior toughness, high mechanical strength, and uniform conductivity to the carbon nanotube wire-like structures derived from the carbon nanotube films and/or yarns. Thus, the touch panel 10 and the display device 100 adopting the carbon nanotube wire-like structures as the first and second conductive layers 122, 142 are durable and highly conductive. Furthermore, since the carbon nanotubes have excellent electrical conductivity properties, each of the first and second conductive layers 122, 142 formed by the plurality of spaced-apart carbon nanotube wire-like structures parallel to each other has a uniform resistance distribution and uniform optical transparency. Thus the touch panel 10 and the display device 100 adopting the carbon nanotube wire-like structures have improved sensitivity and accuracy. Furthermore, since each first-electrode 124 and second-electrode 144 is connected with the end of at least one corresponding carbon nanotube wire-like structure, the determination of the position of the pressing point by detecting the voltage changes between the corresponding pairs of opposite electrodes 124, 144 can be highly accurate. That is, the touch panel 10 and the display device 100 can provide operation with very high precision.

Finally, it is to be understood that the above-described embodiments are intended to illustrate rather than limit the invention. Variations may be made to the embodiments without departing from the spirit of the invention as claimed. The above-described embodiments illustrate the scope of the invention but do not restrict the scope of the invention.